P.C. Rossin College of Engineering and Applied Science

Fine-tuning a rainbow of colors at the nanoscale

What makes those Angry Birds on your favorite digital device so very colorful? Screens of all shapes and sizes use filters to display the breadth of colors. But conventional color filters, typically made of organic dyes or chemicals, are complicated and costly to fabricate, and are susceptible to damage from heat and ultraviolet radiation.

Ph.D. candidate Beibei Zeng leads a Lehigh research team that has developed a more hardy and stable plasmonic color filter (PCF) that approaches the “transmission efficiency” of these convential filters. The group reported its results recently in a paper titled “Ultrathin Nanostructured Metals for Highly Transmissive Plasmonic Subtractive Color Filters,” which was published by Scientific Reports, a publication of the Nature group. The paper was written by Zeng; Filbert J. Bartoli, department chair and professor of electrical and computer engineering and Zeng’s adviser; and Yongkang Gao ‘13PhD.

PCFs are based upon the collective oscillation of electrons at metal/dielectric interfaces. These filters are made by fabricating, on a thin metal film, arrays of holes with diameters of 100 nanometers or less. By varying the geometry of these nanoholes -- their diameter, shape, periodicity and pattern -- it is possible to control the colors that are transmitted and to create transmit a broad spectrum of colors for imaging applications. Until recently, PCFs have been understood to carry a transmission efficiency of around 30%, while conventional filters boasted 80% efficiency. The Lehigh team’s results have more than doubled the efficiency of PCFs, indicating a greater potential role for plasmonics in future display technologies. The group’s paper has been downloaded more than 1,300 times since it was published in October, and it was recently cited in an article published by Nano Letters.